Use ceres' function to convert a string to a solver type
Use ceres' function to convert a string to a solver type

Reviewed By: YanNoun

Differential Revision: D27260952

fbshipit-source-id: c605735d0ce50e9418b552b9f5a3615fc6bacbaf

oscarlorentzon/OpenSfM,oscarlorentzon/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM,oscarlorentzon/OpenSfM,oscarlorentzon/OpenSfM,oscarlorentzon/OpenSfM,mapillary/OpenSfM